Foam polystyrene is commonly known as styrene foam or EPS (expanded polystyrene), which is made by allowing a polystyrene-resin-containing blowing agent such as butane or pentane to expand to about 50-100 times its original size, for example, in a die. In terms of volume, foam polystyrene is 98 percent air, which results in such characteristics as being light in weight and having both heat-insulating properties and strength. Specifically, foam polystyrene's density is 20 kg/m3, and its strength is about 5000 kg/m2. In other words, foam polystyrene is lightweight yet sturdy enough to support weight of 5 tons per square meter. A dome made of this kind of material can retain heat, tolerate shocks such as those from earthquakes, and is comfortable to be inside of. Also, foam polystyrene is useful as a cushioning material because it effectively disperses the force of impacts. Accordingly, one of its well-known uses is for sporting helmets.
In domes made of expanded polystyrene, earthquake-resistant structures having firm foundations have been adopted. For example, as shown in FIG. 4, the foundation of a sectionally assembled dome described in Patent Document 1 is constructed by connecting concrete blocks 80, each of which weighs about 200 kg, and laying them on the ground 70 in a circle. The lower ends of expanded polystyrene 1 segments that make up the dome 60 are fitted into a recess provided at the side of concrete blocks. The inner area of each concrete block is covered by a waterproof membrane, and then concrete 82 is placed on the membrane. This kind of structure, which well withstands earthquake shocks, corresponds to the continuous footing or mat foundation applied to wooden buildings. That is to say, if an earthquake occurs this kind of structure will not collapse, although it might shake violently. However, if a dome is used as a warehouse or the like, shaking due to an earthquake is likely to cause articles to fall off from shelves on which they are stacked. Moreover, if a dome is used as a place of safety, shaking due to an earthquake can cause people who have taken refuge in the dome to feel uneasy. Accordingly, what are required are domes made of expanded polystyrene to resist the shocks that result from earthquakes and to reduce such shaking.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-211444